The present invention relates to rotary position indicators, and more particularly, to a cam arrangement for the familiar rotary position indicator for devices such as valves, switches (both sealed and unsealed) and the like, wherein the rotary position indicator includes a shaft rotatable about its longitudinal axis.
Rotary position indicators are employed to indicate the angular status of a valve or other device that operates on a rotary basis. The output of the rotary position indicator employed may be visual or electrical, depending on the arrangement involved.
As to rotary position indicators having an electrical output, in one embodiment the output is concerned with the opening or closing of a switch contact of a switching arrangement for the opening and closing of the switch as a matter of control of the basic operation involved, with the switch either being of the snap action type or of the reed type typically being employed. In this type of arrangement, the shaft of a rotary position indicator is at least kinematically linked to the shaft of the valve or other rotary mechanism that is involved. Thus, when the shaft of the valve or other such rotary mechanism involved rotates, the shaft of the rotary position indicator rotates. Typically, a camming device is fixed to the rotary position indicator's shaft, and thus rotates when the shaft of the valve or other mechanism involved provides its timing function; the camming device in turn actuates a snap action switch by direct mechanical contact, or a reed switch by magnetic coupling.
Another form of electrical output has to do with the actuation of what is known in the art as a "proximity" switch, which is actuated in a manner similar to a reed switch. The formentioned coupling is achieved by a metallic slug or screw that is secured to the camming device involved. The end result causes the "proximity" switch to open or close during the cycle of operation involved.
The arrangement of the shaft for rotary position indicators normally is of two basic types.
One type is the so called "thru-shaft" type, wherein a solid shaft passes from the enclosure exterior through the enclosure wall and transfers the rotary motion of the device involved in the control system to any switches that are involved. Alternately, a magnetic coupling arrangement is involved, in which a magnet is mounted on the end of the two rotary shafts involved, with such magnets being positioned on each side of the enclosure wall. When the shaft that is exterior of the enclosure wall is rotated, the shaft that is interior of the enclosure wall rotates in a similar manner due to the magnetic coupling involved. The magnetic coupling approach has the advantage of permitting continuous enclosure walls in damp or otherwise hazardous locations.
The general arrangement of this invention is concerned with an adjustable cam arrangement which is adjustable in a single plane, and which allows the user to adjust the cam position relative to the rotary position indicator shaft manually and without the use of tools; thus, it is particularly suitable for "in-field" use.
It has long been known that the cam employed in connection with rotary position indicators must be adjustable so that the components that are involved can be actuated or deactuated at selected degrees over the rotational movement that the rotary position indicator is to have.
Basically, several types of this device are available, as follows:
One such device is that comparable to what is disclosed in U.S. Pat. No. 4,214,133, granted Jul. 22, 1980, which involves a disclosure of several forms of rotary position indicators, with the rotary position indicator involved using a simple collar, which is locked onto the position indicator rotary shaft with a set screw; a second screw is separately inserted into the collar and positioned to actuate a snap action or proximity switch when the shaft is rotated.
Another arrangement employs a 360 degree (360.degree.) spline that is mounted on the rotary position indicator shaft and is locked or keyed into position with a so-called "through" or keying pin. The cam employed in such devices has an offset contoured recess which is intended to mate with said spline, with a shoulder limiting the motion of the cam along the spline; a coil spring supplies the resilient force that seats the cam firmly against the spline. In devices of this type, the actuation point is adjusted by lifting or pressing the cam against the spring until it clears the spline, and then rotating the spline to the desired position and releasing same. This style of rotary position device involves cams that must be supplied in pairs because a second cam assembly must hold the spring in operating position.
A major principal object of the invention is to provide a cam arrangement for the rotary position indicator shaft itself that may be manually operated without tools.
Another object of the invention is to provide a cam arrangement for rotary position indicators that operates to effect adjustment of the control system involved by merely shifting the rotary position indicators shaft cam in a single plane between locking and unlocking relation.
Another major object of the invention is to provide the option of adjusting the position of the rotary position indicator device control cam that is part of the installation, or where or when as needed insofar as "in-field" use is concerned.
Other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings in which like reference numerals indicate like pans throughout the several views.